The invention disclosed and claimed herein pertains generally to a unitized digital meter for selectively measuring unknown values of voltage, resistance and the time duration of an event. More particularly, the invention pertains to a meter of the above type which is of sufficient light weight and compactness to be included as part of a portable test set which is employed to measure multiple parameters or physical quantities associated with an electrical equipment. Even more particularly, the invention pertains to apparatus for selectively measuring a voltage, resistance, or time in response to a set of external binary instructions, and for providing the measured value of a quantity in the form of a digital code.
In order to test the operability of certain electrical or electronic equipments, it is necessary to sequentially measure the values of various parameters or physical quantities associated with the equipments. For example, to determine whether or not a certain Navy missile system is in operable condition, it is necessary to make in excess of 20 discrete measurements of various physical quantities. A number of these measurements are to determine voltage and resistance at different points, and the time duration of certain events, such as the time elapsing between two voltage pulses.
Meters for measuring each of the quantities voltage, resistance and time are of course well known to those skilled in the art. However, it would be extremely advantageous to test the operability of the above missile system in a field location, and a combination of conventional meters for measuring the quantities voltage, resistance and time may be too bulky, fragile, temperature sensitive, or cumbersome to include in a portable test set.
In a test set for making a large number of measurements associated with electrical or electronic equipment it is clearly advantageous to minimize the operator involvement required to obtain the measurements. This advantage may be realized by including a digital system in the test set which provides a set of binary instructions to the test set, whereby a succession of measurements are made automatically. Conventional meters for determining voltage, resistance and time may be unadaptable for control by such binary instructions, and may be unable to provide, without substantial alteration, a measured value in the form of a coded digital signal.